Can blender export files for games, probably for mods?
its done using the fbx file export from blender generally...you'll have to look at what the game engine your looking at wants for setting up stuff within the file in blender, like collision objects names(ends in _ucx for unreal etc.. since blender exports fbx files i know they will go into unreal 4 at least. 

https://docs.blender.org/manual/en/dev/addons/io_fbx.html

for unity
https://answers.unity.com/questions/439807/blender-to-unity-which-export-format-is-best.html

for unreal 4
https://docs.unrealengine.com/en-us/Engine/Content/Types/StaticMeshes/HowTo/Importing
https://docs.unrealengine.com/en-us/Engine/Content/Types/SkeletalMeshes
https://docs.unrealengine.com/en-US/Engine/Content/FBX
https://docs.unrealengine.com/en-US/Engine/Content/QuickStart